How to Build Concrete Retaining Wall Foundations

Several things can cause a retaining wall to fail, but an inadequate foundation is one of the most common. If you hope to make your retaining wall last for more than a year or two, you must do the job right the first time. Building a retaining wall is more than simply stacking a few pavers or bricks on top of one another. You must first create a strong foundation on which to build.

Measuring tape
Spray paint or colored chalk dust
Trench shovel
Level
Concrete
Small trowel or screed
Steel rebar
Mortar
Pavers or bricks

Instructions

- 1
  Measure the width of the bricks or pavers you intend to use with a measuring tape. Add 4 inches to this measurement to find the proper width of the foundation for your retaining wall.
- 2
  Mark the ground where you intend to build your retaining wall. You may spray-paint a line on the ground or use colored chalk dust to outline the area for your foundation.
- 3
  Dig a trench inside the area you just marked using a trench shovel. Use a level to check that the bottom of the trench is not sloped. Keep digging until the trench reaches a depth of approximately 8 inches.
- 4
  Mix a batch of concrete according to the manufacturer's instructions. Continue to stir the concrete until it is completely smooth.
- 5
  Pour approximately 3 inches of concrete into the trench. Spread the concrete evenly along the length of the trench using a trowel or screed, a tool designed for spreading concrete.
- 6
  Lay steel rebar rods on top of the concrete you just poured to reinforce it. Position the bars horizontally inside the trench and space them approximately 4 inches apart. Steel rebar is available in multiple lengths, so you can either buy rods the length of your wall or lay shorter rods end to end inside the trench.
- 7
  Pour another 3 inches of concrete on top of the rebar you just laid.
- 8
  Allow the concrete to set for a full 48 hours before moving on. Once the concrete has set, you can begin constructing your retaining wall by applying a layer of mortar on top of the concrete foundation and starting to lay your first row of pavers or bricks.

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